1. Field of the Invention
The present invention relates to an optical recording and reproducing apparatus having discrete optical pickup heads for simultaneously recording or reproducing information signals such as an audio signal and a video signal to or from two recording sides of an optical medium and, more particularly, to the optical recording and reproducing apparatus for synthesizing the audio and video signals recorded separately to specific tracks on each of the two recording sides by two optical heads to output the reproduced audio and video signal.
2. Description of the Prior Art
When digitally coded audio and video signals or signals with a high transfer rate, such as a High Definition Television (HDTV) video signals, are recorded and reproduced by an optical recording and reproducing apparatus, there is a practical limit to the wavelength of the shortest recordable wave (more specifically, the shortest pit length), and it is difficult to sustain the required transfer rate using only one optical head. This has led to the development of multi-channel heads, or more specifically, an increase in the number of optical heads, to assure the required transfer rate, such as described in the Japanese Laid-open Patent Publication No. 4-170756, published Jun. 18, 1992.
With reference to FIGS. 33, 34, and 35, an optical disk used in such a conventional recording and reproducing apparatus is described. In FIG. 35, a side view of the optical disk 1412 which is rotatably supported by a disk motor 1416 is shown. The optical disk 1412 is comprised of a top member having a top recording side SA and a bottom member having a bottom recording side SB. Above the top side SA, a photo sensor 1427 and a top optical pickup (head) 1406 are placed on substantially the same radial line. Below the bottom side SB, a photo sensor 1428 and a bottom optical pickup (head) 1412 are placed on substantially the same radial line. For recording and reproducing operation, the top and bottom heads 1406 and 1412 move on this radial line inwardly and outwardly, respectively.
In FIGS. 33 and 34, plan views of the top and bottom members (sides SA and SB) are shown, respectively. A recording track is formed on each of the top and bottom sides SA and SB spirally extending in a direction reverse to each of rotating directions Rd2 and Rd1 from the outer to the inner and from inner to the outer circumferences, respectively. These spirally wound recording tracks are divided by radial lines 1601 and 1602 into a plurality of semi-tracks V1 to Vn and V1' to Vn', as shown in FIGS. 33 and 34. Each semi-track stores a semi-frame of the recording information thereon. In this case, the reference symbol for each sector represents the number of semi-frame of the information recorded thereon. The information signal for one frame is separately recorded on a corresponding pair (V1 and V1', for example) of semi-tracks on top and bottom sides SA and SB. In other words, the corresponding pair of semi-track separately provided on the opposite sides SA and SB stores one frame of information signal. Position detection members 1427 and 1429 comprised of a reflecting material are provided on the top and bottom sides SA and SB, respectively.
In FIG. 31, a example of such a conventional recording and reproducing apparatus is shown. The optical recording and reproducing apparatus 1400 has two reading and writing optical heads 1426 and 1412 for simultaneously recording or reproducing the information signals to or from two recording sides SA and SB of the optical disk 1415 rotated by the disk motor 1416. A user can instruct the apparatus 1400 to operate at his desirable operation mode by using a mode set panel 1401. The mode set panel 1401 produces a mode instruction signal Sm1 which is the coded result of the ON/OFF state information of operation keys incorporated in the panel 1401. On receipt of this mode instruction signal Sm1, a mode determiner 1402 determines the control of each element of the optical recording and reproducing apparatus 100 based on the current operation mode and the current condition of the apparatus 100, and produces and transfers an operation mode signal Sm2 to a top head controller 1403, a bottom head controller 1409, a motor controller 1417 for controlling the rotation of the disk motor 1416, a recording signal processor, and a reproduced signal processor 1422.
An original recording signal So is fed to the recording signal processor 1418 through an input terminal 1421. From the signal processor 1418, first and second recording signals Sw1 and Sw2 are transferred to a Sw1 signal processor 1420 and a Sw2 signal processor 1419, respectively, and are further transferred to the bottom and top heads 1412 and 1406. The first and second recording signals Sw1 and Sw2 make a pair of information signal for one frame. Based on these recording signals, the heads 1412 and 1406 write the information signals on the aimed tracks on the sides SA and SB, respectively.
The top and bottom heads 1406 and 1412 also reproduce the first and second information signals Sr1 and Sr2 from the tracks formed on the side SA and SB. These reproduced signals Sr1 and Sr2 also make a pair of information signals Sr for one frame of original signal So. The signal Sr1 thus reproduced by the bottom head 1412 is transferred to the bottom head controller 1409, a Sr1 signal processor 1424, and an ID signal generator 1413. Similarly, the signal Sr2 is transferred to the top head controller 1403, a Sr2 signal processor 1423, and an ID signal generator 140. The signals Sr1 and Sr2 are further transferred to the reproduced signal processor 1422 where the information signal for one frame is completed and output through an output terminal 1425.
Based on the reproduced signal Sr1 and Sr2, the ID signal generator 1413 and 1407 demodulates the ID signals Sd1 and Sd2 including the address data output them to the head controllers 1409 and 1403, respectively.
Based on the position signals which the photo sensors 1426 and 1428 produces with respect to the position detection members 1427 and 1429, V mark detectors 1414 and 1408 produce signals Sv1 and Sv2 indicative of V marks Vm1 and Vm2, respectively. The signal Vm1 (Sv1) is transferred to the Sr1 signal processor 1424 and the Sw1 signal processor 1420, and the signal Vm2 (Sv2) is transferred to the Sr2 signal processor 1423 and the Sw2 signal processor 1419.
Based on these signals Sv1, Sm2, and Sd1, the top head controller 1403 controls the movement of the top head 1406 through a top head driver 1404 and top head actuator 1405. Similarly, the bottom head controller 1409 controls the movement of the bottom head 1412 through a bottom head driver 1410 and a bottom head actuator 1411, based on the signal Sv2, Sm2, and Sd2.
In FIG. 32, the details of the head controller 1403 and 1409, the head drivers 1404 and 1410, the head actuator 1405 and 1411, and the heads 1426 and 1428 are shown. The head controllers 1403 and 1409 have focus controllers 1501 and 1517, tracking controllers 1502 and 1518, and linear motor controller 1503 and 1519, respectively. The head drivers 1404 and 1410 have focus drivers 1505 and 1520, tracking drivers 1505 and 1521, respectively. The head actuators 1405 and 1411 have focus actuators 1507 and 1523, tracking actuators 1508 and 1524, and linear motor 1509 and 1411, respectively. The heads 1406 and 1412 have focus error signal generator 1510 and 1526, tracking error signal generators 1511 and 1527, motor speed signal generators 1512 and 1528, reproduced signal generators 1513 and 1529, laser diodes 1514 and 1530, and input terminal 1515 and 1531, respectively. These are connected to each other by lines or signal line as shown in FIG. 32.
The top tracking controllers 1502 produces a top track jump signal St2, as synchronized with the input of top vertical synchronization signal Sv2, for controlling the head driver 1404 and head actuator 1405 to instruct the top head 1406 to jump over the predetermined number of tracks. Similarly, the bottom tracking controller 1518 produces a bottom track jump signal St1, as synchronized with the input of the signal Sv1, for jumping the bottom head 1412 over a predetermined number of tracks.
In such cases, optical heads are provided discretely for the two recording sides SA and SB of the optical disk 1412 in attempt to increase a transfer rate, however, wherein the operating mode selection timing of the head actuators is not set separately for reading and writing heads 1406 and 1412 each for the side SA and side SB and head B) according to the offset of the signal recording positions on recording sides SA and SB of the optical disk 1412. Therefore, the relationship between the specific combination of track addresses scanned by head 1406 and head 1412 becomes disrupted when changing operating modes. Then, even if the head positions are corrected so that the values of the track addresses output from heads 1406 and 1426 are restored to the specified correlation based on the track addresses reproduced from head 1406 and head 1412, the reproduced image becomes disrupted whenever the timing is offset from the predetermined correlation between the head positions of heads 1406 and 1412, and a reproduced image of consistent quality cannot be obtained.
This problem is described below with reference to FIGS. 36A-36K. Wave lines La, Lb, Lc, and Ld show the top V-mark signal Sv2, the top reproduced signal Sr1, the bottom V-mark signal Sv1, respectively, when the information signals are reproduced without changing operation mode without any problem. These V-mark signals provide the reference for the video signal recording position in each disk track, and one frame of the video signal is divided between the top and bottom heads and recorded between one V-mark signal and the next V-mark signal (for example, video data V3 and V3' are combined to form the video signal for one frame). As a result, the corresponding reproduced signals Sr1 and Sr2 makes a complete pair of the semi-frame signals V3 and V3'.
Wave lines Le, Lf, Lg, Lh, Li, Lj, and Lk show the top V-mark signal Sv2, the bottom V-mark signal Sv1, operation mode signal Sm2, top track jump signal St2, bottom track jump signal St1, the top reproduced signals St2, and the bottom reproduced signal Sr1 when the reproducing mode is changed from "still" to "play" at time T1 by the operation signal Sm2. According to the track jump signal St2, the top head 1406 jumps to the outer track at the position indicated by the radial line 1601 (FIG. 33) where the information semi-frame changes. The bottom head 1412 jumps to the inner tracks at the position indicated by the radial line 1602 (FIG. 34) according to the track jump signal St1. In other word, both the top and bottom heads 1406 and 1412 repeats to scan the current semi-track according to the track jump signals St2 and St1 even when the current semi-track is scanned over.
Therefore, when the reproducing mode (signal Sm2) changes from the "still" to the normal "play" at time T1, the bottom head 1412 reproduces the information of semi-track V1' again. Because the "still mode" remains selected until time T1, the still jump wave form is output when the V-mark signal is detected, and video data V1 is reproduced from the top head again and again. When the still mode OFF command is input at T1 and the still OFF mode is selected, the still jump wave form is not output, and the video data reproduced from the top head advances normally V1, V2, . . . Vn.
Similarly, the correlation between the bottom V-mark signal St1 and the reproduced video signal Sr1. Because the still mode remains selected until time T1, the still jump wave form is output when the V-mark signal is detected, and video data V1' is reproduced from the bottom head again and again. When the still mode OFF command is input at T1 and the still OFF mode is selected, the still jump wave form is not output, and the video data reproduced from the bottom head advances normally V1', V2', . . . Vn'. In this case, the combination of video data output from the top and bottom heads becomes offset from the predetermined combination, e.g., V3 and V2', and the reproduced video is therefore not the correct video.
It should be noted here that double-sided optical disk media are generally manufactured by combining single-sided optical disk media produced in the same manufacturing process. To dynamically balance the disk media when bonding the two single-sided media together, the offset between the vertical synchronization marks of disk SA and disk SB during bonding may range from a maximum 0 (zero) degrees to 360 degrees.
It is therefore possible that a normal reproduction image cannot be obtained by means of the prior art as described above depending upon the timing relative to the V-mark signals of the top and bottom heads at which the operating mode is changed